Basically, Java Management Extensions (JMX) is to management systems what JDBC (Java Database Connectivity) is to databases. Discover why you should use this this powerful technology to serve as a layer between your applications and arbitrary management systems.

This chapter is from the book

This chapter is from the book

The Java Management Extensions (JMX) specification2 defines a Java
optional package for J2SE3 that provides a management architecture
and API set that will allow any Java technologybased or accessible
resource to be inherently manageable. By using JMX, you can manage Java
technology resources. You can also use Java technology and JMX to manage
resources that are already managed by other technologies, such as
SNMP4 and CIM/WBEM.5

JMX introduces a JavaBeans model for representing the manageability of
resources. The core of JMX is the simple, yet sophisticated and extensible,
management agent for your Java Virtual Machine (JVM) that can accommodate
communication with private or acquired enterprise management systems. JMX also
defines a set of services to help manage your resources. JMX is so easy to use
and is so suited for the Java development paradigm that it is possible to make
an application manageable in three to five lines of code.

Basically, JMX is to management systems what JDBC (Java Database
Connectivity)6 is to databases. JDBC allows applications to access
arbitrary databases; JMX allows applications to be managed by arbitrary
management systems. JMX is an isolation layer between the applications and
arbitrary management systems. So why do we need this layer anyway?

2.1 Why We Need JMX

2.1.1 Choosing a Management Technology

As we saw in Chapter 1, many different management technologies are being used
in different areas of the industry. CMIP7 dominates the telephony
management market. SNMP dominates the device and network management market.
Because this book is about developing Java applications and systems, let's
narrow our focus to those technologies used by Java-based resources. Most
Java-based resources today will be part of applications.

Even though SNMP is supported by some applications and middleware, it is not
widely used for application management. One of the most commonly cited reasons
for this is that many application vendors and management vendors have felt that
the granularity of security in SNMP is not sufficient to use it for
configuration updates and sensitive information. Therefore SNMP is often seen as
useful only for read-only management of more or less public data and
events. SNMP also does not have a natural model for operations on managed
resources. Operations must be represented as a settable attribute. Sometimes
this can be a difficult representation to map. Dependencies and associations can
also be difficult to represent in SNMP.

CIM defines a more natural way to represent management data and addresses
some of the weaknesses just described. It has extensive models for systems and
devices, but the application management models are still emerging. The fact
remains that there is no dominant management technology for the management of
applications.

This would not be such a big problem if there were a single, dominant
management systems vendor. If that were the case, you could use the management
technology chosen by that vendor. Unfortunately, life is not that simple. Today
the enterprise and application management market is pretty evenly split between
Tivoli Systems8 and Computer Associates,9 who use their
own proprietary technology for their manager-agent infrastructure.

If you have to manage an application or resource that runs on only one
operating system, or on one vendor's systems, then choosing a management
technology can be guided (or dictated) by the preferences of that vendor.
Microsoft's Windows,10 IBM's AIX,11 Sun's
Solaris,12 and Hewlett-Packard's HP-UX13 each has its
own management system. However, one of the great things about Java has been the
ease in which applications can be ported to and supported on many different
vendors' systems. This means that most Java-based applications run on many
platforms. If you are developing managed software products, you may be pressured
to support multiple management technologies and systems because every vendor
will want you to make your Java resources manageable by its management
system.

Just to add to the list of management technologies you need to support,
customers may have installed enterprise management systems that they will want
to use to manage your application. In fact, they may or may not buy your
application, depending on whether or not it can be managed by their existing
enterprise management software. Your customers cannot be expected to replace
their existing enterprise management systems just to accommodate your
application. If you supply your own management system, your customers may still
not be happy. They may not want yet another management console to watch and
understand just to manage your application. Adding another console mitigates the
console consolidation benefits of their enterprise management systems.

If you are a developer or architect working for a vendor of cross-platform
applications, you will find yourself between a rock and a hard place. The rock
is that your marketplace may be demanding that your software be manageable. To
appease that marketplace, the software will need support for multiple management
technologies. The hard place is that the cost of developing support for one
management technology is expensive. This cost includes the learning curve,
design and development, and maintaining currency with those technologies as they
continue to advance. The cost of developing support for multiple technologies
may very well exceed the potential new sales. This makes the business case for
creating manageable applications and systems very hard to maintain and
contain.

As a result, the potential return on investment may not motivate you to
instrument appropriately for manageability. In fact, you may choose to write
your own application-specific management system to solve a particular problem
quickly, and not implement it for any external management technology. You can
see how this adds to the populations of unique, nonstandard management systems
and unmanageable applications.

A single suite of uniform instrumentation for manageability, like JMX, makes
it cost effective to develop new applications with management capability. You
can use JMX to instrument your Java applications. You can also use JMX to
provide access to the manageability capabilities of your non-Java applications
via Java Native Interface (JNI) and wrappers. Because JMX is centered on an
architecture for pluggable adapters that allow any management technology to
manage your resources, you have the best of both worlds: instrumenting your
application with one management technology, and being manageable by many
different management systems.

2.1.2 Dealing with Diversity

One of the primary challenges in managing applications is their diversity.
This diversity is also a challenge for developers! Applications today vary
widely in purpose, size, architecture, and criticality. Very little is common
across all application types. Application architecture trends are increasing the
diversity rather than settling the industry on a few de facto standard
approaches.

JMX can be used to enable management of a wide variety of application
architectures. JMX allows you as a developer to build your skills on one
management technology that you can then apply to lots of application projects,
today and in the future. Using JMX to enable this variety of application types
benefits management systems vendors as well. They can support JMX well and be
able to manage a wide variety of applications. Some of the application types
that JMX is suited for are centralized applications, distributed applications,
Internet applications, e-business applications, and service-oriented
applications.

2.1.2.1 Centralized Applications

Centralized applications, such as payroll and accounting, are backed by a
database on a high-end server and usually accessed by a limited set of users,
like a financial department. Managing centralized applications entails ensuring
high availability and performance throughput because they can be a single point
of failure. The clients of these distributed systems are usually other programs,
which expect lightning-fast response times.

2.1.2.2 Distributed Applications

Distributed applications, such as mail systems, usually require groups of
small and midrange server systems to be running at all times, and they are
accessed throughout the enterprise. Managing distributed applications is often a
scaling problem: Many, many servers must be managed (i.e., available, connected,
and performing well), as well as the networks that connect them, in order to
simply ensure the application is available to its users. Generally the clients
require proprietary software, so client software distribution and configuration
must be managed as well.

2.1.2.3 Internet Applications

The introduction of the intranet/Internet concept precipitated a new class of
application that connects the end user to existing, traditional, centralized
applications. The new application facilities range from Web-accessible corporate
personnel directories to Web-based order-tracking systems that benefit customers
and reduce order management costs. These types of applications make it easier to
access corporate information inside traditional applications, and they reduce
the number of personal contacts necessary. Managing Internet applications
entails keeping several layers of applications available to each other and the
network: Web servers, application servers, back ends. Browsers must be
appropriately configured.

2.1.2.4 E-Business Applications

The next generation of autonomous, Web-based applications is rapidly being
developed and deployed in the new business environment. These applications
embody e-commerce in the form of catalogs, shopping, marketplaces, and auctions.
The move of the supply chain to the Internet will drive the next set of
critical, distributed business-based applications. These applications move the
heart of the businessbuying supplies and selling productsto the
Internet. Managing e-business applications is challenging because applications
may span enterprise boundaries and use unreliable protocols like HTTP.

2.1.2.5 Service-Oriented Applications

Service-based architectures are currently emerging where IT resources across
the network appear, move, and disappear. Relationships between applications can
be just-in-time and fleeting. Managing the dynamic topologies, dependencies, and
availability of these applications in this environment will be difficult at
best.

Each of these classes of applications has its own management challenges.
However, all of these application types execute across multiple hosts, operating
systems, and corporations. They incorporate existing traditional and emerging
application models. They are no longer just client-server, they are now
client-middleware-server. These new application types are business critical,
creating the need for them to be uniformly controlled and managed by a
business's existing management systems with the same diligence as
traditional applications. JMX is flexible and extensible enough to be taken
advantage of in all of these diverse types of application architecture.

2.1.3 Being Managed by Multiple Management Applications

As we discussed in Chapter 1, there are many different types of management
applications: distribution, inventory, topology, configuration, operations,
event, automation, monitoring, and performance. You will probably want your
application to be managed by several of these. Without JMX, you might have to
implement explicit support for each type of management application. If
you're using JMX combined with JMX adapters, the same instrumentation can
be used to support and interact with most or all of these applications.

2.1.4 Supporting Application-Specific Management Systems

Your application will need to be installed, configured, monitored, and
maintained. This means that you must implement your own management
systemthat is, an application-specific management systemthat
supports these tasks. Otherwise, you will be dependent on a management system
being available in your customer's environment. This dependency may limit
sales if some of your customers have a different management system, or even no
management system. Applications in the market today have their own proprietary
instrumentations to communicate with their internal management systems, as well
as instrumentation to connect to other management systems. We've seen how
JMX can be used to interact with multiple management technologies and management
applications. In the same vein, JMX can be used to drive an internal or
application-specific management system, as well as an external management
system.